1. Field of the Invention
The present invention relates to an information storage system having a high-efficiency information transfer function. The above information transfer function may be an information transfer function for transferring data from an information storage medium such as a magneto-optical disc to a mother information processing system. In particular, the present invention improves an advance reading function previously proposed by the inventor of the present invention so that the advance reading function may be used more effectively.
2. Related Art
An information storage system in the related art includes a control unit for reading data out from a information storage medium and writing data thereinto and a data buffer memory. The control unit, according to an amount of information to be transferred specified by a mother information processing system, transfers data previously stored in the information storage medium using the data buffer memory.
Such an information storage system may be a disc apparatus such as a magneto-optical disc apparatus and constitutes a filing system together with a mother information processing system such as a host adapter including a SCSI.I/F unit.
Such an information storage system in the related art is idle after completing a specified information transfer work until subsequent information is specified by the mother information processing system. Thus, the efficiency of the information storage system is degraded.
The inventor of the present invention has proposed the advance reading function, as mentioned above, used in an information storage system which has also been proposed by the inventor, as an information storage system controller' in Japanese Patent Application No. 4-280671. The proposed advance reading function actively uses an idle time such as that mentioned above generated after the information storage system has completed a specified information transfer work. More particularly, the advance reading function, after the information storage system has completed the specified information transfer work, reads data blocks subsequent to the data blocks which have been transferred in the above specified information transfer work, in advance of subsequent information being specified by the mother information processing system. The advance reading function then stores the thus read data blocks into a spare-data storage memory. Then, if the above mother-system'subsequent specified information includes a work of reading data blocks out from the information storage medium, which data blocks are identical to the data blocks previously stored in the spare-data storage memory as mentioned above, the previously stored data blocks may be transferred to the mother system immediately after the relevant information is specified. Thus, the information processing efficiency may be improved.
However, the information storage system previously proposed by the inventor stops such an advance reading operation immediately after the system receives subsequent information specified by the mother system which does not specify that the same advance reading operation is to be continued, and thus the information storage system performs the work thus specified by the mother system instead of performing the advance reading operation. Thus, the advance reading function may not always be used effectively.